Regular syringes that do not have a force-amplification structure are typically held by the user between the index and middle fingers whereas the thumb applies a linear force to the syringe plunger over a distance. When significant forces are not required, such a syringe is associated with accurate aiming of the substance to be dispensed and full control of the dispensing, since the motion of the thumb coincides with the line of the plunger's movement.
However, the dispensing of sticky and/or viscous materials from a syringe requires the application of a significant force to the plunger of the syringe. Depending on the viscosity of the dispensed material and the amount of this material, the user may experience difficulties in generating, maintaining and/or controlling such a force for the necessary period of time. As a consequence, an inadequate or poorly controlled force and/or the user's fatigue results, particularly when a need arises to use a syringe repetitively, lead to undesirable, inaccurate results.
Some devices operative to amplify an input force are configured with a pistol-type handle having an attached lever which amplifies the force of the person's hand and applies it to the plunger of a syringe. During the use of such a pistol-type force amplifying device with a syringe, the line of movement of the plunger is located above the user's hand, and the distribution of substance exiting from the syringe occurs when the user squeezes the lever of the syringe force amplifying device. This configuration does not allow accurate aiming of the substance and hampers dispensing, especially in applications where such a delivery of substance occurs in tight areas with limited visibility. These conditions can be encountered in numerous industries including, but not limited to, medical procedures, such bonding fractured bones or cementing ruptured spinal disks, as well as soldering paste dispensing in fabrication of electrical and electronic equipment.
Also known is a force amplifying device that engages a syringe in-line with the syringe wherein the length of the driving member of this device must be equal to the length of the syringe plunger rod or longer in order for the syringe-engaging rod plunger to travel the entire [content containing] length of the syringe barrel and to expel all of the substance from it, adding significant size to the combination of the syringe and force amplifying device, so that the whole arrangement substantially long, typically unnecessarily impeding the precise positioning of the syringe tip prior to and during substance dispensing.
It is, therefore, desirable to have a simple force amplifier configured to provide accurate and convenient dispensing of substance while not requiring the exertion by the user of significant loads along the user axis of motion.